The invention relates to improvements in paper machine press rolls, and more particularly to an improved press roll with a drilled hole pattern in the surface that attains improved dewatering of a web passing through a press couple formed between two press rolls.
The invention relates to a press roll primarily as used in a press couple where opposed parallel rolls pass a felt and a web therebetween to press water from the web into the felt. The roll backing the felt may be provided with various configurations to relieve the resistance to water flow and accept water being pressed into and through the felt. If no such means are provided, the roll is generally referred to as a plain roll, but the rolls with relieving openings are grooved rolls, blind drilled rolls, fabric sleeve rolls and suction rolls. While such rolls are presently currently used in roll couples, they may also be employed in extended nip presses where one side of the nip is faced by an arcuate shoe or belt creating a pressing zone against the surface of the roll.
A requirement of a roll in a dewatering press is that it function to transfer the maximum amount of water from a web to a felt passing through the nip, and this is accomplished by offering a minimum amount of resistance to the transfer of water. This must be done uniformly so as not to mark the web, and must be done with a minimum amount of rewetting on the offrunning side of the nip.